The present invention relates to a storage controller and a bus control method for use therewith. More particularly, the invention relates to a bus control method and a storage controller with which the bus control method is implemented. The method of the invention dynamically controls the mode of bus utilization within the storage controller in accordance with the operation mode of the computer system connected to the controller.
The storage controller located between the central processing unit (CPU) and a storage device controls data transfer therebetween in response to input/output requests from the CPU. Recently, the so-called multi-processor method has found its way into a growing number of storage controller installations for higher throughput and higher reliability. In such cases, the common bus connection scheme for connecting the component processors constituting the storage controller is known to offer good functional expandability. Two kinds of data are transferred over the bus: control data required by the storage controller for processing the input/output requests from the CPU, and ordinary data exchanged between the CPU and the storage controller.
One conventional example of the multi-processor type storage controller utilizing the common bus connection scheme is the file controller described in "FUJITSU, VOL. 42, No. 1, pp. 12-20 (1991)." This file controller has its component functions divided into a plurality of modules each of which has a microprocessor assigned to it. These modules are connected by a common bus. Each module and the common bus are multiplexed to provide higher reliability.
Conventional storage controllers which adopt the common bus utilization mode are matched to the principal mode of the computer system to which they are connected. For example, computer systems for primarily performing online processing must ensure sufficient responsiveness during operation and therefore adopt a common bus utilization mode that emphasizes control data transfer throughput. On the other hand, computer systems for carrying out batch processing frequently handle large quantities of data and thus adopt a common bus utilization mode that emphasizes data transfer throughput.